Morphology, kinetics and secretory activity of antibody-forming cells

Experimental plasmacytomagenesis in mice

This article discusses some of the mechanistic aspects of plasma cell tumor development. Plasmacytomagenesis, much like other forms of neoplastic development, is a highly complex process that develops in the B cell differentiation lineage. As more is learned about the molecular genetics of multiple myeloma and PCTs in mice, a unifying concept will emerge that possibly can explain the phenotypic differences in the two neoplastic cell processes as variants of a common process.

Antibody secreting cells as specific probes for antigen identification

Parasite specific antibody probes were prepared by harvesting lymphocytes from infected tissue and incubating them in vitro to allow the spontaneous secretion of antibodies in the culture medium by antibody secreting B cells present in the lymphocyte cultures. The culture supernatant was then used to screen Western blots of parasite antigens and resulted in the detection of antigens specific for the parasite stages present in the tissue at the time of sampling. Similar antigen recognition patterns were also observed when the cells were taken from the draining lymph nodes but the same pattern was not observed with serum taken from the same animal. The use of antibody probes obtained from in vivo induced antibody secreting B cells (ASC probes) offers a unique and universal approach to study local antibody recognition during infection.

Penetration, clearance and retention of antigen en route from the gingival sulcus to the draining lymph node of rats

We investigated the penetration and clearance of antigen in the rat gingiva and the antigen-specific antibody response in the draining lymph nodes. Rats were primarily immunized into the alveolar submucosa with horseradish peroxidase (HRP) in complete Freund's adjuvant. Ultrastructural demonstration of antigen and specific antibody was performed by incubation of cryosections in an HRP solution, followed by peroxidase cytochemistry. Anti-HRP antibody-containing cells were observed in the draining lymph nodes from 2 to 9 weeks after immunization. The bulk of these cells were located in the medullary cords. The extracellular antibody and antibody-containing cells were also found in germinal centers (GCs) from 3 to 9 wk, and 3 wk, respectively, after immunization. The results suggest that the specific antibody response was most enhanced 3 wk after primary immunization. Therefore, at this time we further challenged rats with the topical application of HRP to the gingival sulcus. The results showed that antigen penetrated through the junctional epithelium into the underlying connective tissue and from here was cleared by macrophages or via the lymphatics. In the draining lymph nodes, antigen first appeared in the subcapsular sinus and eventually became retained within GCs. Between 3 and 5 days, the GCs of challenged rats contained more mature-type anti-HRP antibody-containing cells than those of non-challenged rats. The sequence of events observed suggests that antigen challenge applied topically to the gingival sulcus can induce the active GC reaction in the draining lymph nodes of immunized rats.

Immunoglobulin isotype influences traffic of B lymphocytes through popliteal lymph nodes in sheep

The antigen specificity of blast B lymphocytes was used to trace their passage from blood through antigenically naive popliteal lymph nodes in sheep. Ovine popliteal nodes selectively recruited lymphocytes containing IgG1 in preference to those containing IgG2. This selection appeared to operate at the level of the vascular endothelium. Stimulation of lymph nodes with killed S. aureus and dextran sulphate (DXS) (which promotes an antibody response in ovine lymph nodes biased in favour of IgG2) did not significantly alter this pattern.

Hymenolepis citelli, H. diminuta and H. microstoma: immunoglobulin-containing cells in the lamina propria of the mouse gut during primary and secondary infections

The indirect immunofluorescent technique was used to determine the occurrence of IgA, IgM and IgG1 immunoglobulin-containing cells in local intestinal mucosal immune responses to Hymenolepis citelli, H. diminuta and H. microstoma infections in mice. In the intestinal lamina propria of H. citelli and H. diminuta infected mice there was no increase in the mean numbers of immunoglobulin-containing cells when compared with uninfected control mice, but there was in H. microstoma infected mice. The numbers of IgG1- positive cells in both infected and uninfected mice were very small relative to IgA and IgM immunocytes. The distribution of immunocytes in the lamina propria of infected and uninfected mice was essentially similar and the localization of isotypes in duodenal sections showed no immunoglobulins in the villous epithelial cells. There was also no marked difference between primary and secondary infections indicating that immunoglobulin-containing cells play no major role in functional immunity against hymenolepid infections in the mouse. The presence of IgA and IgM was also demonstrated on the tegument of the tapeworms, although the distribution was patchy and more abundant on H. microstoma than on H. diminuta or H. citelli. The time of appearance of both isotypes was latest on H. citelli.

The "in situ" immune response in lymph nodes: a review

For many years data on the development of specific antibody-forming cells in lymph nodes were incomplete, fragmentary, and even contradictory. A number of recent studies have been performed, concerning 1) their overall architecture; 2) migration of B-lymphocytes; 3) localization of accessory cells and T-lymphocytes which are believed to be involved in humoral immune responses; and 4) localization patterns of specific antibody-forming cells developing during thymus dependent and thymus independent immune responses. Comparison of these new results with those of earlier studies suggests a single route of migration followed by all cells which will differentiate into antibody-forming cells. During their differentiation into antibody-forming plasma cells, antigen reactive B-cells migrate along the required accessory cells and/or T-lymphocytes.

The early postnatal development of the primary immune response in TNP-KLH-stimulated popliteal lymph node in the rat

The popliteal lymph nodes were removed from young rats of various ages five days after a single immunization with TNP-KLH in the hind footpads. Cryostat sections of the lymph nodes were investigated by means of enzyme- and immunohistochemical techniques at the light-microscopical level. The presence and localization of anti-TNP antibody-containing cells were examined using a new technique to visualize specific antibodies. Moreover, the development of the lymph nodes following exogenous antigenic stimulation was compared with that of unstimulated lymph nodes. Specific antibody-containing cells could not be found before day 15 after birth, in rats immunized at day 10. From that time these lymphoid cells were located primarily at the border between cortex and medulla. Younger popliteal lymph nodes showed only aspecific immunoglobulin-containing lymphoid cells. With age, the number of specific antibody-containing cells tended to increase. These cells were more mature, according to morphological criteria and were located nearer the medulla. The first primary follicles were seen at day 19, as was the case in unstimulated animals. The first secondary follicles, containing germinal centers, were detected at day 23, whereas in unstimulated popliteal lymph nodes they were never found. Trapping of immune complexes could not be demonstrated before day 33 after birth. The later appearance of this phenomenon might be a consequence of the techniques applied to demonstrate specific antibody-containing cells.

Distinct short-lived and long-lived antibody-producing cell populations

This report analyzes the life span of Ig-containing cells (IgCC) in different sites of antibody production. The experimental approach was based upon the observations that most IgCC are derived from proliferating precursors while IgCC themselves are mainly nondividing end cells. Rats were given a continuous infusion of [3H] thymidine via an osmotic pump inserted in the peritoneal cavity. At intervals of 1, 3, 5 or 10 days after starting infusions, tissues were taken and analyzed by a combination of immunohistology and autoradiography to identify the proportions of IgCC which had gone through S phase of the cell cycle during the period of infusion. After 3 days infusion the median and (range) percent-labeled IgCC in the medullary cords of mesenteric and cervical lymph nodes and the red pulp of the spleen were, respectively, 88 (81-90), 75 (66-77) and 88 (82-93). Conversely that for IgCC in bone marrow was only 13 (11-17) and that in the lamina propria of the jejunum 47 (33-68). The rate of increase in labeling of bone marrow IgCC with length of infusion was approximately linear. Extrapolation of this slope suggests that bone marrow IgCC have a life span in excess of 3 weeks. The slopes of increase in IgCC labeled with time for lymph nodes and spleen were clearly biphasic suggesting that while most IgCC in these tissues have a life span of less than 3 days, there is also a minor population of long-lived IgCC. The lamina propria appears to have approximately equal proportions of long and short-lived IgCC. The life span of IgCC, with the exception of IgMCC, appears to be a feature of the site of antibody production rather than the Ig class produced. Almost all IgM-containing cells were found to be short lived.

Antigen-driven selection of virgin and memory B cells

This review has summarized the evidence indicating that far more B cells are produced in adult bone marrow than are required to maintain B cell numbers in the periphery. It is shown that most if not all these newly-formed B cells have the potential to become mature peripheral B cells. However, to do this they need to receive an appropriate signal in secondary lymphoid organs. Cells failing to receive such a signal die after a brief period. Two separate situations have been identified which result in recruitment of newly-formed virgin B cells into the peripheral B-cell pool: Following activation by antigen. When the peripheral B-cell pool has been depleted. It is proposed that the first of these signals requires T help and is initiated by antigen presented on interdigitating cells in extrafollicular areas of secondary lymphoid organs. This process seems to be confined to periods immediately following administration of antigen and does not continue in established immune responses to thymus-dependent antigens. It seems probable that continued B cell activation, occurring during long term antibody responses, takes place in the follicles of secondary lymphoid organs and is driven by antigen presented on follicular dendritic cells. Indirect evidence is cited which suggests that somatic mutation in rearranged immunoglobulin V-region genes occurs mainly following B-cell activation in follicles and not during primary B lymphopoiesis. It is suggested that this may involve a hypermutation process which is switched on in activated B cells in germinal centers. Evidence is presented suggesting that plasma cells generated from B cells activated early in immune responses have an average life-span of less than 3 d. However, plasma cells generated in established responses appear to have an average life-span in excess of 20 d. Later sections in the review consider how B-cell recruitment in thymus-independent antibody responses differs markedly from recruitment during thymus-dependent responses. The possible role of splenic marginal zone B cells in some thymus-independent antibody responses is discussed and the evidence indicating that SIgM + ve, IgD-ve marginal zone B cells develop as a distinct population from recirculating SIgM + ve, IgD + ve B cells is summarized.

Binding of different antigen-enzyme and antibody-enzyme conjugates by intracellular antibodies in cytoplasm and Golgi complex of plasma cells. A double immunocytochemical study

Intracellular immunoglobulins in plasma cells were characterized by antigen-enzyme conjugates and anti-immunoglobulin antibody-enzyme conjugates applied in a double immunocytochemical approach. After their assemblage, immunoglobulins in the cytoplasm of anti-TNP anti-body producing plasma cells can be demonstrated both by TNP-enzyme conjugates and by anti-immunoglobulin (mu or gamma chain specific) antibody-enzyme conjugates. Once arrived in the Golgi complex (GC) detection with TNP-enzyme conjugates remains possible, but anti-immunoglobulin anti-body-enzyme conjugates did not bind to a detectable degree. Similar results were obtained in experiments where immunoglobulin-enzyme conjugates were used both as an antigen-enzyme conjugate and as an antibody-enzyme conjugate.